Differential Air Pressure Switch. Operating range 0.07 to 12 inches W.C. Switch action spdt two position. Responds to positive or negative pressure. Electrical: 15 amp 125/250/277 vac. Junction box has standard 7/8” opening for conduit. Includes 12” of ¼" plastic tubing and compression fittings. Includes 2” of 3/8” tubing that works as a sleeve over the ¼" tubing. Overall size 6 x 4½ x 3" (including mounting bracket). Includes 2 mounting screws. Must be mounted in the vertical position.